[Bug 88012] [bisected BYT] complete freeze after: drm/i915/vlv: WA for Turbo and RC6 to work together

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88012

--- Comment #117 from John <jbmacbrodie at yahoo.com> ---
I've been running several days without a freeze on my 4.2.6 kernel.  I simply
added intel_idle.max_cstate=1 to my kernel arguments, no other power arguments,
and no more setting GPU frequency caps.  

intel_idle.max_cstate=0 was effective too, but my system ran warm (not hot)
when idle.  At max_cstate=1 the case temperature seems normal to me.

I suspect that the cost of this work-around would be less battery run time. 
But until the T100CHI has full hardware support in linux (no sound, no
bluetooth...), I'm tethered to a powered hub anyway.

I've also tested versions of 4.1.13, 4.2.6, 4.3, even 4.4-rc1 without obvious
side-effects.  4.4rc2 did freeze within minutes of booting, but 4.4-rcx has too
many regressions (no wifi even on a dongle) to take that freeze seriously.

I also tried max_cstate=2 on my Dell laptop (baytrail) but that seemed to
trigger a "not quite" freeze during a kernel build (fan speed malfunction
typical of a freeze, but the build finished successfully.)  The subsequent
power down crashed and the next boot was extremely difficult to start (press
hold repeat).  I'm not going to try the remaining max cstates 3-6!  

This might suggest the freeze lies in handling cstates 2-6 starting after
kernel-3.16.7.  But that assumes this bandaid lasts more than another week.

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